Digital circuit for impedance spectroscopy
An impedance measurement system with a frequency sweep has been developed. A sinewave generator provides an excitation signal to be injected in the system to be measured. The resulting current and voltage are acquired and a synchronous demodulation allows to precisely select the frequency to be analysed and to determine the system's response.
The system is controlled by a PC via an Ethernet link. The user can choose the frequency range and step for the analysis. The system is made out of two boards: one for the measurement itself and one for the Ethernet communication.
The analysis can range from 0.1 Hz to 2 MHz with the first version of the acquisition board. A second board allows to work up to 50 MHz. The sweep time can be varied, it is of the same order fo magnitude as the period corresponding to the smallest frequency analysed. Excitation and acquired signals hav a range of ± 2.048 V. Different injection and measurement circuits have been developed, depending on the application.
The case occupies a volume of 13 x 18 x 14 cm3.